182 THE INDUCTIONS OF BIOLOGY. 



care, however, to restrict its meaning. If we simply substi- 

 tute the term polarity, for the circuitous expression the 

 power which certain units have of arranging themselves 

 into a special form, we may, without assuming anything 

 more than is proved, use the term organic polarity or po- 

 larity of the organic units, to signify the proximate cause 

 of the ability which organisms display of reproducing lost 

 parts. 



66. As we shall have frequent occasion hereafter to refer 

 to these units, which possess the property of arranging 

 themselves into the special structures of the organisms 

 to which they belong ; it will be well here to ask what 

 these units are, and by what name they may be most fitly 

 called. 



On the one hand, it cannot be in those proximate chemical 

 compounds composing organic bodies, that this specific polar- 

 ity dwells. It cannot be that the atoms of albumen, or fibrine, 

 or gelatine, or the hypothetical protein -substance, possess 

 this power of aggregating into specific shapes ; for in 

 such case, there would be nothing to account for the unlike- 

 nesses of different organisms. Millions of species of plants 

 and animals, more or less contrasted in their structures, 

 are all mainly built up of these complex atoms. But if the 

 polarities of these atoms determined the forms of the or- 

 ganisms they composed, the occurrence of such endlessly 

 varied forms would be inexplicable. Hence, what we may 

 call the chemical units, are clearly not the possessors of this 

 property. 



On the other hand, this property cannot reside in what 

 may be roughly distinguished as the morphological units. The 

 germ of every organism is a microscopic cell. It is by 

 multiplication of cells that all the early developmental changes 

 are effected. The various tissues which successively arise 

 in the unfolding organism, are primarily cellular ; and in 

 many of them the formation of cells continues to be, through- 



